SOLUTION: An arch in a memorial arch, having a parabolic shape, has a height of 30 feet and a base width of 40 feet. Find the equation of the parabola which models this shape, using the ๐

Algebra ->  Quadratic-relations-and-conic-sections -> SOLUTION: An arch in a memorial arch, having a parabolic shape, has a height of 30 feet and a base width of 40 feet. Find the equation of the parabola which models this shape, using the ๐      Log On


   

Question 1184545: An arch in a memorial arch, having a parabolic shape, has a height of 30 feet
and a base width of 40 feet. Find the equation of the parabola which models
this shape, using the ๐‘ฅ โˆ’axis to represent the ground.
Answer by MathLover1(20850) About Me  (Show Source):
You can put this solution on YOUR website!

given:
a height of 30+feet=> vertex is at (0,30)
and a base width of 40 feet=> since vertex at x=0, a base width of 40 is the distance between x=-20 and x=20

Solution:
The equation is y=Ax%5E2%2B30
It passes (0,30) and (-20,0) and (20,0)
0=A%2A20%5E2%2B30
A+=+-3%2F40
So the equation is y=-%283%2F40%29x%5E2%2B30